The field of art to which this invention pertains is aqueous thickening and gelling agents.
The use of polygalactomannans as thickening agents for aqueous compositions and to crosslinking such compositions with potassium pyroantimonate and other crosslinking compounds is well known.
U.S. Pat. No. 3,794,115 describes a method for making plugs in boreholes using guar gums as the thickening agent and various crosslinking agents, such as borax glass, sodium and potassium pyroantimonate, antimony oxide and chromium salts. The crosslinking agents are said to have at least one characteristic which can delay the crosslinking action. This characteristic can be that the crosslinking agent is in a slowly soluble form. It can be that the crosslinking agent must react with another component of the dispersion before it has crosslinking capacity. The delaying characteristic may be that at certain pH values the crosslinking action of a particular crosslinking agent is very slow. Finally, the characteristic can be that the crosslinking agent is temperature dependent.
The crosslinking activity of pyroantimonate ions is pH sensitive and occurs in the range of about 3 to 7. At the pH range of 6 to 7, however, the crosslinking activity is very slow. Various acids, such as acetic, citric, oxalic, hydrochloric, sulfuric and nitric acids can be used to control the pH according to U.S. Pat. No. 3,794,115.
In U.S. Pat. No. 3,523,048, bulk delivery of aqueous slurry explosives containing gelling agents is described. Guar gum and potassium pyroantimonate are disclosed as being the preferred gel system. To control the rate of gelation, the pH of the composition is adjusted with various acids, such as fumaric acid, acetic acid, citric acid, nitric acid, sulfonic acid, hydrochloric acid and the like.
U.S. Pat. No. 4,021,355 describes fracturing fluids for oil wells. Potassium pyroantimonate is used to crosslink guar gum at a pH of 5 or below. Sodium dihydrogen citrate is added as an acid buffer to lower the pH of the system and to increase the rate of the crosslinking reaction.